Liquid immersion optical tool, method for cleaning liquid immersion optical tool, and method for manufacturing semiconductor device

ABSTRACT

There is disclosed is a liquid immersion optical tool, which comprises a light source, an optical lens system, a stage which moves an object base on which an object is to be placed, a head comprising a liquid immersion medium fluid supply device and a liquid immersion medium fluid discharge device to provide a layer of liquid immersion medium fluid between the optical lens system and the object, a fence which limits a region of the layer of liquid immersion medium fluid, and a cleaning device which cleans a portion having been contacted with the liquid immersion medium fluid by means of a cleaning solution.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2004-258676, filed Sep. 6, 2004, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid immersion optical tool, a method for cleaning the liquid immersion optical tool, and a method for manufacturing a semiconductor device, wherein a liquid immersion medium fluid layer is provided between an optical lens system and an object, improving an optical performance.

2. Description of the Related Art

A liquid immersion microscope or a liquid immersion exposure tool and the like is used as a liquid immersion optical tool for immersing liquid immersion medium fluid between an object and an optical lens system, thereby improving a resolution and a depth of focus. In a liquid immersion microscope, a liquid immersion medium liquid such as oil or water is provided between an objective lens of the microscope and an object, thereby improving a resolution and a depth of focus. In a liquid immersion exposure tool for use in a semiconductor lithography process, a liquid immersion medium fluid is provided between a lens and a wafer, thereby making it possible to increase NA (Numerical Aperture) and to increase a depth of focus. This exposure tool is expected to be a main exposure tool in manufacturing a semiconductor device in a generation following a 65 nm half pitch generation (WO 99/49504).

The lens of the liquid immersion optical tool is in contact with liquid immersion medium fluid for a long time when the liquid immersion optical tool is used. Thus, there is a problem that substances generated from the tool, the object surface, and a structure for guiding the liquid immersion medium fluid react with each other to adhere to the lens so that the lens surface is clouded. This clouding of the lens surface is problematic because it degrades the resolution and the luminescence.

In addition, there is a problem that the substance or impurities adhered to the lens or members of the tool contaminate the object surface.

In addition, portions having been contacted with the liquid immersion medium fluid include a liquid immersion head, an object stage, and a liquid immersion medium fluid supply and discharge device. There is a problem that, when the liquid immersion optical tool is used for a long time, impurities adhere to their associated portions, and the adhered impurities reach an object and contaminate the object surface.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided a liquid immersion optical tool comprising:

a light source;

an optical lens system;

a stage which moves an object base on which an object is to be placed;

a head comprising a liquid immersion medium fluid supply device and a liquid immersion medium fluid discharge device to provide a layer of liquid immersion medium fluid between the optical lens system and the object;

a fence which limits a region of the layer of liquid immersion medium fluid; and

a cleaning device which cleans a portion having been contacted with the liquid immersion medium fluid by means of a cleaning solution.

According to a second aspect of the present invention, there is provided a cleaning method in the liquid immersion optical tool comprising a light source; an optical lens system; a stage which moves an object base on which an object is to be placed; a head comprising a liquid immersion medium fluid supply device and a liquid immersion medium fluid discharge device to provide a layer of liquid immersion medium fluid between the optical lens system and the object; a fence which limits a region of the layer of liquid immersion medium fluid; and a cleaning device which cleans a portion having been contacted with the liquid immersion medium fluid by means of a cleaning solution,

wherein the portion having been contacted with the liquid immersion medium fluid is cleaned for a predetermined time by means of the cleaning device.

According to a third aspect of the present invention, there is provided a semiconductor device manufacturing method in which a semiconductor device is manufactured by using a liquid immersion exposure tool, the liquid immersion exposure tool comprising:

a light source;

an optical lens system;

a stage which moves an object base on which an object is to be placed;

a head comprising a liquid immersion medium fluid supply device and a liquid immersion medium fluid discharge device to provide a layer of liquid immersion medium fluid between the optical lens system and the object;

a fence which limits a region of the layer of liquid immersion medium fluid; and

a cleaning device which cleans a portion having been contacted with the liquid immersion medium fluid by means of a cleaning solution.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a view showing a configuration of a liquid immersion exposure tool according to a first embodiment of the present invention;

FIG. 2 is a view showing an example of a cleaning device according to the first embodiment of the present invention;

FIG. 3 is a view showing another example of the cleaning device according to the first embodiment of the present invention;

FIG. 4 is a view showing another example of the cleaning device according to the first embodiment of the present invention;

FIG. 5 is a view showing a configuration of a liquid immersion exposure tool according to a second embodiment of the present invention; and

FIG. 6 is a view showing a configuration of a liquid immersion exposure tool according to a third embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

First Embodiment

FIG. 1 is a view showing an outline configuration of a liquid immersion exposure tool according to a first embodiment of the present invention. A reticle stage 31 is provided under a lighting optical system (light source) 20. A reticle 32 which is a photo mask is placed on the reticle stage 31. The reticle stage 31 is movable in parallel to an object base 37 (i.e., in a horizontal direction in the exposure tool). A projection lens system (optical lens system) 33 is provided under the reticle stage 31. The object base 37 is provided under the projection lens system 33. A semiconductor substrate 10 is placed on the object base 37. The heights of the surface of the semiconductor substrate 10 and part of the object base 37 near the semiconductor substrate 10 are almost equal to each other. The object base 37 is movable together with a stage 34 and the semiconductor substrate 10 in the parallel direction and the orthogonal direction to the reticle stage 31 (i.e., horizontal and vertical directions in the exposure tool). The stage 34 can be inclined with respect to the horizontal plane.

A fence 35 is mounted at the lower part of the projection lens system 33. A liquid immersion medium fluid supply and discharge mechanism is provided at the side of the projection lens system 33. The supply and discharge mechanism comprises a pair of liquid immersion medium fluid supply and discharge devices 36 which supply liquid immersion medium fluid into the fence 35, and discharge the liquid immersion medium fluid from the fence 35. A structure of the liquid immersion medium fluid supply and discharge mechanism is not limited to this structure. When one of the pair of liquid immersion medium fluid supply and discharge devices 36 functions as a liquid immersion medium supply device, the other liquid immersion medium fluid supply and discharge device functions as a liquid immersion medium discharge device. That is, the pair of liquid immersion medium fluid supply and discharge devices 36 functions complementarily with respect to the supply and discharge of the liquid immersion medium fluid. During exposure, a space between the substrate 10 and the projection lens system 33 surrounded by the fence 35 is filled with a layer of liquid immersion medium fluid, for example, water, supplied from one of the liquid immersion medium fluid supply and discharge devices 36. Light of exposure emitted from a light source 20 reaches the semiconductor substrate 10 placed on the object base 37 via a mask pattern (i.e., a semiconductor element pattern) of the reticle 32, the projection lens system 33 and the liquid immersion medium fluid layer. In this manner, an image of the mask pattern of the reticle 32 is projected on a photo resist film provided on the semiconductor substrate 10 so that a latent image is formed on the photo resist film. A structure formed of the fence 35 and the pair of the light immersion medium fluid supply and discharge devices 36 is called a head.

A pair of cleaning devices 38 are connected to a pair of the liquid immersion medium fluid supply and discharge devices 36 in order to defog the projection lens system 33 and remove impurities adhered at the time of exposure. The pair of the cleaning devices 38 complementarily supply a cleaning solution into the fence 35 via the pair of the liquid immersion medium fluid supply and discharge devices 36. After exposure, the cleaning solution is supplied into the fence 35, whereby parts or portions having been contacted with the liquid immersion medium fluid supplied from the liquid immersion medium fluid supply device 36 are cleaned.

In a step and scan type exposure tool, all of the patterns on a photo mask are not collectively transferred to a resist laminate film. Only a pattern portion of the entire pattern of the photo mask, which is smaller than the entire pattern of the photo mask, is collectively transferred. The pattern portion is a slit shape predetermined area called an exposure field. Exposure is carried out in a state in which the photo mask and the substrate are moved at a rate according to a magnification of the projection optical system, whereby the photo mask and substrate are scanned by light ray to project the entire pattern of the photo mask onto the resist laminate film. The term “exposure field” may mean the predetermined area of the slit shape on the substrate plane which is optically conjugate with the pattern side on the photo mask.

A photo mask movement distance is greater than a substrate movement distance. Thus, in general, the number of photo mask movements is reduced in order to reduce an exposure process time. Therefore, it is general that relative movement directions of the photo mask and substrate are opposite to each other between the unit exposure regions in which the exposure sequence is continuous.

The relative movement directions (scan directions) of the photo mask and substrate are changed depending on the unit exposure regions. Therefore, the supply/discharge functions of the pair of the liquid immersion medium fluid supply and discharge devices 36 are complementarily changed to be supply/discharge according to the scan direction so that an orientation of the liquid immersion medium fluid flow is changed. In addition, it is possible that one of the cleaning devices 38 is operated according to the scan direction so that a cleaning solution may be supplied from the one cleaning device 38 into the fence 35 via the corresponding liquid immersion medium fluid supply and discharge device 36, and the liquid immersion medium fluid supply and discharge device 36 connected to the other inactive cleaning device 38 is operated so that the cleaning solution after used may be discharged from the fence 35 by means of the other liquid immersion medium fluid supply and discharge device 36.

A pattern region on the photo mask may be restricted by means of a diaphragm called a mask blind. A region of a resist film on which a latent image corresponding to the mask pattern on the photo mask is to be formed (unit exposure region) may be called an exposure shot.

Now, cleaning after exposure will be described. Function water such as ozone water, ionized water, carbonated water, or peroxide water is used as a cleaning solution. Alternatively, acid is used as a cleaning solution. However, when acid is used as a cleaning solution, the lens surface is corroded so that the lens performance may change. Thus, it is preferable that function water be used as a cleaning solution. In addition, cleaning may be carried out by using water vapor.

The cleaning solution is supplied into the fence 35 in a state in which cavities are provided. It is preferable that the cavities be micro-cavities whose average in diameter is 1 μm or less. The micro-cavities have long service life, and are unlikely to disappear before they reach the top of the substrate.

An ultrasound wave, a water jet, or a cavitation jet can be used in order to generate cavities in a cleaning solution. For example, cavities are generated in the cleaning solution by means of a cavitation jet nozzle shown in FIG. 2 or a venturi tube shown in FIG. 3. In FIG. 2, reference numeral 41 denotes a high pressure water nozzle from which a high pressure cleaning solution flows; reference numeral 42 denotes a low pressure nozzle from which a low pressure cleaning solution flows; and reference numeral 43 denotes a mixing portion. In FIG. 3, reference numeral 44 denotes a low speed flow section, and reference numeral 45 denotes a high speed flow section.

The cavitation jet nozzle of FIG. 2 is disclosed in detail in transactions of Japanese Machinery Society (Edition B), Volume 67, Issue 653 (2001-1), pp. 88, Transaction No. 00 to 0620. In general, cavitation jet cleaning is a cleaning method efficiently utilizing a physical force from which there occurs a cavitation phenomenon usually desired to be avoided in fluid engineering. If a pressure lower than a saturated vapor pressure is generated in fluid, cavities occur. The cavities are destroyed if the pressure in the fluid is returned to a pressure higher than the saturated vapor pressure, and at this time, a high pressure is momentarily generated.

The cavitation jet shown in FIG. 2 is designed so that a speed difference in water flow occurs on a boundary between the high speed water discharged from the high pressure nozzle 41 and the low speed water discharged from the low pressure nozzle 42.

The venturi tube 38 of FIG. 3 can be used as a device for generating cavities. When a fluid passes from a nozzle 44 having a large aperture via a nozzle 45 having a small aperture, cavities occur in the fluid, since the speed of the fluid changes from a low speed at the nozzle 44 to a high speed at the nozzle 45.

In addition, a Pitot tube of FIG. 4 can be used as a device for generating cavities. In FIG. 4, reference numeral 46 denotes a high pressure nozzle, and reference numeral 47 denotes a low pressure nozzle.

During cleaning, a cleaning solution containing cavities is supplied from the cleaning device 38 into the fence 35, while the stage 34 on which the semiconductor substrate 10 is placed is moved and accordingly the semiconductor substrate 10 is moved. Cleaning is carried out while moving the semiconductor substrate 10, thereby making it possible to clean parts or portions having been contacted with the liquid immersion medium fluid used during exposure. The parts or portions having been contacted with the liquid immersion medium fluid include the projection lens system 33, the fence 35, the object base 37, the stage 34, and the liquid immersion medium fluid supply and discharge devices 36.

Now, a cleaning period will be described. For example, after exposure has been carried out for a predetermined time, a cleaning process is carried out. In one option, a measuring instrument for measuring intensity of light transmitting the projection lens system 33 (exposure light wavelength is preferable) is provided at the liquid immersion exposure tool, and the light intensity is measured by means of the measuring instrument after exposure has started so that a cleaning process may be carried out when the measured light intensity becomes smaller than a preset value. In another option, in addition to the above-described measuring mechanism, there are further provided: a computing mechanism for computing a lowered quantity of light intensity from information on the light intensity measured by the measuring mechanism; and a calculating mechanism for calculating a cleaning period from the computed lowered quantity of light intensity, for carrying out the cleaning process in a computed cleaning period.

In addition, after the cleaning process has been carried out, a rinse process may be carried out by using a rinse solution in which no cavities exist. By supplying the rinse solution, the cleaning solution which remains in the liquid immersion exposure tool can be removed. Water is used as a rinse solution. For example, by supplying water as a rinse solution from the liquid immersion medium fluid supply and discharge device 36, the inside of the liquid immersion exposure tool is rinsed, thereby removing the cleaning solution which remains in the liquid immersion exposure tool.

A cleaning process is carried out by the above-described cleaning device, thereby making it possible to remove the cloudiness of the lens and to recover the resolution and luminescence. In addition, the substance or impurities adhered to the lens or members of the tool during exposure can be removed, and an object surface can be restricted from being contaminated.

In addition, the liquid immersion exposure tool comprises a cleaning device, thereby making it possible to facilitate a cleaning process and to reduce a maintenance time. By reducing the maintenance time, an equipment operation time is enhanced, and a manufacturing cost of a manufactured semiconductor element can be reduced.

Second Embodiment

The present embodiment shows an example which is different from that of the liquid immersion exposure tool shown in FIG. 1. FIG. 5 is a view showing a liquid immersion exposure tool according to a second embodiment of the present invention. The same elements are designated by the same reference numerals. A duplicate description is omitted here.

In the liquid immersion exposure tool shown in FIG. 5, a cleaning device 58 is provided to be opposed to a substrate face of the projection lens system 33. The cleaning device 58 is detachable from the liquid immersion exposure tool.

Third Embodiment

The present embodiment shows another example which is different from that of the liquid immersion exposure tool shown in FIG. 1. FIG. 6 is a view showing a liquid immersion exposure tool according to a third embodiment of the present invention. The same elements are designated by the same reference numerals. A duplicate description is omitted here.

In the liquid immersion exposure tool shown in FIG. 6, a cleaning device 68 is provided at the back surface of the stage 34, and the cleaning device 68 moves together with the stage 34.

According to the above-described embodiments, an optical lens system and a liquid immersion medium fluid discharge device or the like configuring the liquid immersion exposure tool can be cleaned, and the cloudiness of the optical lens system can be prevented. In addition, the impurities reaching an object surface are reduced, thereby making it possible to prevent contamination on the object surface.

While the above embodiments have described examples of the liquid immersion exposure tool, the above-described cleaning device is provided at a liquid immersion type microscope for observing a surface of an object, and a cleaning process may be carried out. Further, the above-described cleaning device is provided at a liquid immersion type measuring instrument for measuring a surface of an object, and a cleaning process may be carried out. That is, the above-described cleaning device is provided at any liquid immersion type equipment, and a cleaning process may be carried out.

In addition, while, in the above embodiments, water has been used as a liquid immersion medium fluid used during liquid immersion, a liquid immersion medium fluid other than water may be used.

Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. 

1. A liquid immersion optical tool comprising: a light source; an optical lens system; a stage which moves an object base on which an object is to be placed; a head comprising a liquid immersion medium fluid supply device and a liquid immersion medium fluid discharge device to provide a layer of liquid immersion medium fluid between the optical lens system and the object; a fence which limits a region of the layer of liquid immersion medium fluid; and a cleaning device which cleans a portion having been contacted with the liquid immersion medium fluid by means of a cleaning solution.
 2. The liquid immersion optical tool according to claim 1, wherein the portion having been contacted with the liquid immersion medium fluid is one or more selected from the group including the optical lens system, the fence, the object base, the stage, the head, the liquid immersion medium fluid supply device, and the liquid immersion medium fluid discharge device.
 3. The liquid immersion optical tool according to claim 1, wherein the cleaning device generates cavities in the cleaning solution.
 4. The liquid immersion optical tool according to claim 3, wherein an average diameter of the cavities is equal to or smaller than 1 μm.
 5. The liquid immersion optical tool according to claim 1, wherein the cleaning device has any of a cavitation jet, a venturi tube, a Pitot tube, and a ultrasound generator, and the cavities are generated by any of the cavitation jet, the venturi tube, the Pitot tube, and the ultrasound generator.
 6. The liquid immersion optical tool according to claim 1, wherein the cleaning device is connected to the liquid immersion medium fluid supply device.
 7. The liquid immersion optical tool according to claim 1, wherein the cleaning device is loaded on the stage.
 8. The liquid immersion optical tool according to claim 1, wherein the cleaning device is detachable.
 9. The liquid immersion optical tool according to claim 1, wherein the cleaning solution is one selected from the group of function waters including ozone water, ionized water, carbonated water, and peroxide water.
 10. The liquid immersion optical tool according to claim 1, wherein the cleaning solution is acid.
 11. The liquid immersion optical tool according to claim 1, wherein the cleaning solution is water vapor.
 12. The liquid immersion optical tool according to claim 1, further comprising a measuring mechanism which measures intensity of light transmitting the optical lens system.
 13. The liquid immersion optical tool according to claim 12, further comprising: a computing mechanism which computes a lowered quantity of light intensity from information on the light intensity measured by the measuring mechanism; and a calculating mechanism which calculates a period of cleaning by the cleaning device from the computed lowered quantity of light intensity.
 14. The liquid immersion optical tool according to claim 1, wherein a predetermined pattern is transferred to the object by using the optical lens system.
 15. The liquid immersion optical tool according to claim 14, wherein the predetermined pattern is a pattern of a semiconductor element.
 16. The liquid immersion optical tool according to claim 1, wherein a surface of the object is observed or measured by using the optical lens.
 17. A cleaning method in the liquid immersion optical tool comprising a light source; an optical lens system; a stage which moves an object base on which an object is to be placed; a head comprising a liquid immersion medium fluid supply device and a liquid immersion medium fluid discharge device to provide a layer of liquid immersion medium fluid between the optical lens system and the object; a fence which limits a region of the layer of liquid immersion medium fluid; and a cleaning device which cleans a portion having been contacted with the liquid immersion medium fluid by means of a cleaning solution, wherein the portion having been contacted with the liquid immersion medium fluid is cleaned for a predetermined time by means of the cleaning device.
 18. The cleaning method according to claim 17, wherein a rinse process is carried out by means of a rinse solution in which no cavities exist, after cleaning by the cleaning solution is carried out for the predetermined time.
 19. The cleaning method according to claim 18, wherein the rinse solution is water.
 20. A semiconductor device manufacturing method in which a semiconductor device is manufactured by using a liquid immersion exposure tool, the liquid immersion exposure tool comprising: a light source; an optical lens system; a stage which moves an object base on which an object is to be placed; a head comprising a liquid immersion medium fluid supply device and a liquid immersion medium fluid discharge device to provide a layer of liquid immersion medium fluid between the optical lens system and the object; a fence which limits a region of the layer of liquid immersion medium fluid; and a cleaning device which cleans a portion having been contacted with the liquid immersion medium fluid by means of a cleaning solution. 